Sounds like an old Honda Trail 110 (1982 thru 1986) or 90 (1968 thru1979) would work. In low range they go super slow and climb well. In hi range they go about 47 mph wound out. Great gas mileage, 200 ish pounds, excellent rear luggage rack you can augment with a milk crate, etc. Auto clutch, 4-speed tranny, step-thru, 65 million made (sold world wide thru 2010 but only thru 1986 in North America) so parts are available from aftermarket suppliers.
Note that the 1980 110 did NOT have a hi-low range tranny so I’d avoid them. 1981 was a transition year as well. They are two models I’d avoid. Also pre-1968 had leading link front suspension and used two rear sprockets vs a sub-transmission for hi-low range so not near as easy to go to low range…15 minutes to change over.
But either get one in good running shape or prepare to learn to replace parts. U-tube is your friend if you choose a beater. They are small for a large person but the original poster is a small guy.
Note that the new Trail 125 version sold today is over 260 pounds and does NOT have the dual range transmission....and is quite pricey.